Wisconsin’s redistricting case is headed back to a three-judge panel — but it will consist of a slightly different set of judges.

Barbara Crabb, a U.S. district judge for Wisconsin’s western district, on Thursday withdrew from the case without explanation. She will be replaced by U.S. District Judge James Peterson, a colleague in her district who was randomly assigned to the case.

The case centers on whether legislative maps that GOP lawmakers drew in 2011 are so beneficial to Republicans that they violate the voting rights of Democrats.